1. Field of the Invention
The present invention relates to a plasma device.
2. Description of the Related Art
Recently, accompanying the increase in chip size of ULSI (ultra large scale integrated circuits), there has also been a tendency to increase the diameter of a silicon substrate used as a substrate for the ULSI. Since sheet leaf processing for handling substrates one at a time has become mainstream, if the substrate is increased in diameter there is a need for high speed processing of at least 1 mm per minute in order to maintain high productivity if etching and film forming are carried out. In a plasma device for handling an increased diameter substrate enabling high speed processing, it is essential to be able to generate high density plasma having an electron density in excess of 1011 cm−3 and to obtain the flow of a large quantity of gas in order to efficiently remove a large amount of reaction products discharged from the substrate surface as a result of the high speed processing. In order to enable the generation of high density plasma, a parallel plate type plasma device introducing a magnetic field has been developed. As a conventional plasma device of this type, a magnetron plasma etching device using a dipole ring magnet is disclosed in, for example, Japanese Patent Laid Open No. Hei. 6-37054.
FIG. 43 is a schematic diagram of the conventional magnetron etching device using a dipole ring magnet. FIG. 43(a) shows the state at the time of etching, and FIG. 43(b) shows the state at the time of conveying the substrate. In the drawings, reference numeral 4301 is a vacuum vessel, reference numeral 4302 is an electrode I, reference number 4303 is a substrate in a space 4315, reference number 4304 is a gas introduction opening, reference numeral 4305 is a show plate, reference numeral 4306 is a dipole ring magnet, reference numeral 4307 is a bellows, reference numeral 4308 is a substrate conveying port, reference numeral 4309 is a gate valve, reference numeral 4310 is a substrate conveying port, reference numeral 4311 is a gas outlet, reference 4312 is a vacuum pump, reference numeral 4313 is a matching circuit and reference numeral 4314 is a high frequency power source.
At the time of etching, source material gas that has been introduced from the gas introduction opening 4304 is discharged from a plurality of small holes in the shower plate 4305. This source material gas and reaction product gas discharged from the substrate surface as a result of the etching reaction are discharged to the outside, through a side section of the electrode I 4302, the porous plate 4308 and the gas outlet 4311, by the expel pump 4312. The porous plate 4308 causes a lowering of the gas conductance between a space above the substrate 4303 and the gas outlet 4311, and is provided so as to make the gas flow substantially uniformly in a direction of rotation of the space above the substrate 4303. Since the gas is made to flow uniformly in a direction of rotation of the space above the substrate 4303, the gas conductance between the space above the substrate 4303 and the gas outlet 4311 is inevitably restricted and there is a problem that a large amount of gas can not flow. As a result, in high speed etching on large diameter substrates the etching rate is lowered, and a problem arises that the etching shape degenerates.
At the time of conveying the substrate, the position of the electrode I 4302 is lowered, as in FIG. 43(b), and the substrate is conveyed through the gate valve 4309 and the substrate conveying port 4310 using an external substrate conveyance machine. The bellows 4307 are required in order to cause the electrode I 4302 to move. At the time of plasma generation, power loss occurs due to high frequency current flowing in the bellows 4307, and there is a problem that the high frequency output power of the high frequency power source 4314 can not be efficiently supplied to the plasma. There is also a problem that a complex structure is required because the electrode I 4302 is made to move.
A device using electron cyclotron resonance (ECR) is also known as a plasma device using microwaves. This device enables excitation of high density uniform plasma on a substrate, but since the method involves high density plasma being excited locally, caused to widely diffuse within the container and uniformly supplied onto a object to be treated, installation of a shower plate is difficult, and it is difficult to promptly remove gases that are reaction by-products.
As a high density plasma device using microwaves, a device using a radial line slot antenna is also known (Japanese patent laid-open No. Hei. 8-111297). However, if this device is put to practical use, it is not always possible to cause high density plasma to be generated stably over a long period of time. Also, the conditions for causing the generation of plasma are not definite.
The object of the present invention is to provide a plasma processing device, within a narrow space inside a container that enables uniform formation of a high quality thin film on a large substrate at a low temperature and at high speed, by causing excitation of uniform high density plasma having a low plasma potential over a large surface area, making supply of source material gas uniform, and swiftly removing reaction by-product gases by adopting a structure equivalent to a shower plate. The invention is applicable to plasma processing other than an etching plasma process.